A Tale of Two Species: Speculation on the Introduction of Pachycereus pringlei in the Sierra Libre, Sonora, Mexico by Homo sapiens

摘要

We passed binoculars back and forth, hardly believing that the enormous, multi-armed cactus towering over the dense thornscrub on the far side of the canyon was a sagueso (Pachycereus pringlei), Saguesos (also called cardones) are giant cacti of the Gulf Coast of Sonora, seldom existing more than a few kilometers from the Gulf of California except for some populations living on hillsides two hundred fifty kilometers to the northwest, the northern limit of its range, Yet here, far inland, more than forty kilometers from any other known specimen was asagueso more than twelve meter s tall. The sagueso is highly selective, living in a narrow band along the Sonoran coast from roughly fifty kilometers south of Guaymas to approximately forty kilometers north of Puerto Libertad, a total distance of less than three hundred kilometers (Figure 1). The great cacti are prototypical creatures of the dry Gulf Coast region of the Sonoran Desert (Shreve and Wiggins, 1964), a region in which average rainfall seldomexceeds 200 mm and frequently is less than 100 mm They never venture into the habitats Shreve labeled Plains of Sonora or the Foothills of Sonora.